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Your opinion on adding weight to improve landings


Scott Lee

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I added 30 pounds per side in the baggage compartment using ankle weights to see if landings were easier with a little more weight.  I know increased weight decreases stall speed but it seems to make the plane more stable on approach in gusty conditions.

 

Anyone else tried this?  What do you folks think?

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In theory, weight added aft of the cg moves the cg rearwards and should make the plane less stable, not more.

 

As an aside, moving the cg aft also should increase overall performance. The thought is that the farther aft the cg, the less tail down force is needed, so the wings have to produce slightly less lift to counteract it and so less induced drag.

 

Possibly apocryphal tales of Mooney salesman sliding their seats back to eke out just a few extra knots! Easy to demonstrate in still air - trim for level flight, then slide the seat back - you will need to trim nose down a hair and you will pick up a knot or two. Downside is the plane is slightly less dynamically stable in pitch.

 

And, of course, all of the above involves checking carefully to see the plane is within cg limits.

 

Also, increased weight increases stall speed - I assume you misspoke there.

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Yep, I know increased weight increases stall speed, not decreases.  (Need more lift)  I'm recovering from having the flu so my brain is a bit fuzzy.  Or I could blame my fat fingers.

 

I put the boxes of weights on the floor right behind the seats (20lb then 10lb) on both sides.  I didn't notice any difference in takeoff performance.

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Yep, I know increased weight increases stall speed, not decreases.  (Need more lift)  I'm recovering from having the flu so my brain is a bit fuzzy.  Or I could blame my fat fingers.

 

I put the boxes of weights on the floor right behind the seats (20lb then 10lb) on both sides.  I didn't notice any difference in takeoff performance.

 

When you added dead weight to the plane you also needed to either increase speed and/or angle of attack to generate the lift needed to stay airborne.

 

Increasing speed makes landing more difficult if much faster than the 1.3*Vso formula.  Likewise increasing angle of attack brings you closer to stall.  Both are bad.

 

What landing issue are you trying to solve?  What do you not like about your landings?

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When you added dead weight to the plane you also needed to either increase speed and/or angle of attack to generate the lift needed to stay airborne.

 

Increasing speed makes landing more difficult if much faster than the 1.3*Vso formula.  Likewise increasing angle of attack brings you closer to stall.  Both are bad.

 

What landing issue are you trying to solve?  What do you not like about your landings?

 

Wait a minute here.

 

While it's true that increased weight increases AoA and stall speed...who cares?  The airplane is within CG and still under gross weight.  The POH stall speeds are given at GROSS WEIGHT and inside the CG envelope.  So if anything, he's just moving closer to book values.

 

The problem he's trying to solve is a real one -- the CT is a very light airplane, and at light weights is very susceptible to wind effects.  It also doesn't want to "sit" well at low weights and high (30-40 degree) flap settings.  The CT does feel more stable and may be "easier" to land at higher weights.  I think if Scott likes the handling of the airplane at higher weights, what he's doing when flying solo is completely appropriate.

 

Scott, another possible location for the weight is under the seats, which is closer to the center of CG than the baggage bay.  You might have to rig up something to keep the weight from shifting, especially if you have an AP servo under the pilot seat.  maybe use sandbags instead of metal weights?  That said, there is nothing wrong with were you are putting the weights now, other than the CG moving slightly aft.

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Wait a minute here.

 

While it's true that increased weight increases AoA and stall speed...who cares?  The airplane is within CG and still under gross weight.  The POH stall speeds are given at GROSS WEIGHT and inside the CG envelope.  So if anything, he's just moving closer to book values.

 

The problem he's trying to solve is a real one -- the CT is a very light airplane, and at light weights is very susceptible to wind effects.  It also doesn't want to "sit" well at low weights and high (30-40 degree) flap settings.  The CT does feel more stable and may be "easier" to land at higher weights.  I think if Scott likes the handling of the airplane at higher weights, what he's doing when flying solo is completely appropriate.

 

Scott, another possible location for the weight is under the seats, which is closer to the center of CG than the baggage bay.  You might have to rig up something to keep the weight from shifting, especially if you have an AP servo under the pilot seat.  maybe use sandbags instead of metal weights?  That said, there is nothing wrong with were you are putting the weights now, other than the CG moving slightly aft.

 

No. The heavier he makes the plane the more difficulty he will have landing it...esp if he screws around with CG.  He will need more power and fly faster when he flys heavy )or increase his angle of attack) and it will be harder to manage on approach and in his turns.

 

I am more curious what he thinks his landing issues are than arguing over W&B.   You and I both know landing the FD is not difficult if you learn to finesse the stick and flare properly...the biggest problem with the plane is the odd site picture given the short nose and the high wing which reduces ground effect lift and drag.

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A heavy CT lands  much easier and handles much better heavy. I have flown CT's up to 1500 lbs and they are much easier to work with. Being light makes the controls much more sensitive. You almost can't get a CT out of CG unless you stick a little tiny 90 lb. person solo  in the cockpit or throw lead in the tail. Us earlly CT fliers talked about it at nauseum in 2006, but quit because it was never an issue.

Unless you have flown a CT at 1450+ lbs you have no idea. I would say try it before you comment. I especially like it on windy landings.

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The POH stall speeds are given at GROSS WEIGHT and inside the CG envelope.  

 

Close.

 

POH stall speeds are in fact at Maximum Gross Weight, but are with the cg at the forward limit - the least favorable condition.

 

Rest sounds about right!

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Even with the weights I am well inside the CG envelope - I'm 200lb, carry between 15-20 gal of fuel and flying solo.

 

The problem I'm trying to help with is stability in gusty conditions.  I get my longitudinal alignment right on the center line and a gust comes along right before touch down and pushes me off to one side.  In moline it's not a big deal the runways are enormous, 150 feet wide. Another time I had the right wheel on the ground and a left gust picked up the high wing and I thought I would flip over.  Almost filled my pants.  

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BTW I could try moving the weights under the seats, they are the strap on leg weights filled with sand so they would lie flat.  I left them in the box because I was concerned about the possibility of them shifting around in the baggage compartment.  If I was doing a cross country with my wife the weights would be replaced by luggage, so I thought - whats the difference?  I picked 30 lbs per side to stay under the 50 lb max.

 

I put them in the baggage compartment for a second reason, in level flight I have to trim a bit nose down, if I try to fly level I gain altitude.

 

Thanks,

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I would want to become proficient at flying/landing a plane anywhere within the plane's envelope.

 

Adding weight like this seems to be a bit of a band aid approach to what may be a different problem.

 

Maybe there is something so bizarre and difficult about how a CT lands at light weight that added ballast is a practical solution. My actual time in CT's is quite limited, so I'll let others speak to that.

 

But overall this is a pretty unusual approach when dealing with a plane loaded anywhere in its cg envelope.

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I would leave them in the baggage. Like I said before a little aft CG in the CTLS will help on landings.

 

As for getting blown off the centerline the weight is not going to help much. It is a piloting thing. You are just going to have to get used to recognizing and making the corrections a little quicker

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My CT is far more difficult to land when I'm solo, low fuel and no baggage.  I think the extra difficulty is weight related not balance.

 

The lowered stability shows itself at round out and after, I'm more prone to balloon and more prone to realize rapid sink.  Another issue are thermals on final are harder to descend through.

 

 

...  I had the right wheel on the ground and a left gust picked up the high wing and I thought I would flip over.  Almost filled my pants.  

 

We get shear here that can produce left and right gusts in the same area at the same time but that's a pretty rare condition most places.  If the gusts are from the left its the left wheel you need to get on the ground 1st.  Better to have the stick into the wind then to wait till the wrong side settles 1st.

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Even with the weights I am well inside the CG envelope - I'm 200lb, carry between 15-20 gal of fuel and flying solo.

 

The problem I'm trying to help with is stability in gusty conditions.  I get my longitudinal alignment right on the center line and a gust comes along right before touch down and pushes me off to one side.  In moline it's not a big deal the runways are enormous, 150 feet wide. Another time I had the right wheel on the ground and a left gust picked up the high wing and I thought I would flip over.  Almost filled my pants.  

 

Okay, you are having xwind problems. 

 

The best way to land the CT in xwind and xwind gusts is with a forward slip all the way from the top of the approach to touchdown on one wheel.  The plane is so nimble and the stall speed so low you can get away without crabbing and using a slip all the way.   When you turn to final do a cross-control setup with the upwind wing dipped toward the direction of xwind using aileron and point the nose at the runway using the opposing rudder.   Stabilize the approach, level and  flare as normal.

 

You can go no flaps if you want to keep your speed up.  The max xwind is 16kts with zero flaps.  Because it's a high wing you don't need to worry about touching a wing tip on the runway, but you do want to make sure you stay aligned using rudder or you will side-load.

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The time I had the scare the wind sock was blowing from the right so that was why I was putting the right wheel down.  Then I got a gust from the left which raised that wing.  It felt like the left wing was straight up.

 

I'll try the forward slip idea.

 

thanks,

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The time I had the scare the wind sock was blowing from the right so that was why I was putting the right wheel down.  Then I got a gust from the left which raised that wing.  It felt like the left wing was straight up.

 

I'll try the forward slip idea.

 

thanks,

what flap setting were you using?

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Rear CG should lower the stall speed a little, and make it fly slightly faster. However, adding more weight to get the rear cg might offset the lower stall speed. I wonder what the ratio is there... obviously it depends on where the weight is... a touch of weight in the back of the tail might actually lower the stall speed, but 50 lbs of cargo in the cargo hold might still have a higher stall speed due to the overall weight going up. My plane lands "nicer" with some weight in the rear cargo area as well...

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1) As a reminder, side slips and forward slips are identical aerodynamically. The only difference is the flight path over the ground.

 

2) Yes, what is being described is a side slip. Nothing fundamentally wrong with an extended side slip on final, but beware that some planes limit extended slips, most often due to issues with the unporting of fuel pickups. Not sure if this is the case with a CT, but I can see how it might be in a low fuel situation. Furthermore, extended uncoordinated flight can feel disconcerting to passengers.

 

Hence, I think they are the exception, rather than the rule.

 

Most pilots will fly final in a crab, then gradually transition to the required side slip during the roundout and flare. It's important that this skill is honed, and not become too mechanical - ground friction has a way of reducing or even eliminating the crosswind component in the flare.

 

Finally, if anyone came to me asking for help when landing light, my automatic response would be to suggest some dual. NOT adding ballast. But That's Just Me, speaking as a one time flight instructor - so I may be a bit biased.

 

Finally, finally, for those times you DO need ballast, collapsible water containers are a good option. If a new loading at any point makes that ballast unnecessary or problematical, just dump the water! As usual, just make sure any weight/ballast is secured - you do NOT want it shifting around!

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It's important that this skill is honed, and not become too mechanical - ground friction has a way of reducing or even eliminating the crosswind component in the flare.

 

 

Here's an example:

 

 

Strong, gusty crosswind with a crab angle held until the roundabout, and then the crosswind virtually disappearing, due to ground friction and the trees on the upwind side of the runway.

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1) As a reminder, side slips and forward slips are identical aerodynamically. The only difference is the flight path over the ground.

 

 

 

In most cases wouldn't the flight path be the same and heading be different? Most all of my slips side or forward are over the centerline or extended centerline.

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In most cases wouldn't the flight path be the same and heading be different? Most all of my slips side or forward are over the centerline or extended centerline.

 

 

I see what you mean and see where the confusion "slips" in!

 

Below, you are correct that the flight paths are the same:

 

Slips.gif

 

I guess what I was getting at was in the side slip you are intentionally moving through the air sideways to stay lined up with something - in this case the runway.

 

In the forward slip, heading is not considered, so you are moving through the air as uncoordinated as possible to lose altitude - though on landing your flight path is in fact the same - staying on the runway centerline.

 

So, you are correct and I expressed it poorly.

 

The first diagram below shows what I was trying to say:

 

Slipping.gif

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